Fix date range for last month date filter.  TMP-57.

I couldn't get any of the search results (even before my changes) returning any output but I printed the result of the date range changes and that was all correct.  Also did all my playing with moment.js to get that right on a separate unrelated file.  Tested against months with 30, 31 days and also February.  Also checked January to ensure rollover to previous year / month worked and it's all fine.  Richie maybe you could give me a hand when you have time to see why the search isn't working on my machine anyway, cheers :)